Hydraulic fuse

ABSTRACT

A hydraulic fuse includes a body defining a cylindrical bore therethrough. A tubular piston including a radially extending opening therein is located in the cylindrical bore of the body and is resiliently biased to a normally open position. The tubular piston member is of low mass and is movable against the force of a resilient biasing means in response to fluid flow quantities above a predetermined maximum. During movement of the tubular piston against the force of the resilient biasing means the internal wall of the cylindrical bore partially closes the radial opening in the tubular piston member thereby increasing the pressure drop across the piston member and further urging the piston member to move to a no-flow or closed position. The tubular piston member may be provided with a pilot flow opening therethrough so that a predetermined quantity of flow may exist across the piston member when the radial opening therein has been completely closed.

United States Patent [191 Jackson 1 June 26, 1973 HYDRAULIC FUSE HarryYale Jackson, Cherry Hill, NJ.

[73] Assignee: Eaton Corporation, Cleveland, Ohio [22] Filed: July 29,1971 [21] Appl. No.: 167,311

[75] Inventor:

3,464,439 9/1969 Budzich .II. 137/504 Primary Examiner-Henry T.Klinksiek Assistant Examiner-Robert J. Miller Attorney-Teagno & Toddy[57] ABSTRACT A hydraulic fuse includes a body defining a cylindricalbore therethrough. A tubular piston including a radially extendingopening therein is located in the cylindrical bore of the body and isresiliently biased to a normally open position. The tubular pistonmember is of low mass and is movable against the force of a resilientbiasing means in response to fluid flow quantities above a predeterminedmaximum. During movement of the tubular piston against the force of theresilient biasing means the internal wall of the cylindrical borepartially closes the radial opening in the tubular piston member therebyincreasing the pressure drop across the piston member and further urgingthe piston member to move to a no-flow or closed position. The tubularpiston member may be provided with a pilot flow opening therethrough sothat a predetermined quantity of flow may exist across the piston memberwhen the radial opening therein has been completely closed.

5 Claims, 1 Drawing Figure --IIllllIl.-

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. INVENTOR. HARRY YALE JACKSON ATTORNEY g// LL Q/ HYDRAULIC FUSEBACKGROUND OF INVENTION 1. Field of Invention This invention relates toa hydraulic flow control valve. More particularly this invention relatesto a highly accurate and responsive flow control valve.

2. Discussion of the Prior Art Hydraulic fuses of the type designed forthe purpose of preventing or restricting fluid flow through a line uponthe occurrence of an excessive flow rate are known in the art.Illustrative of devices of this type are the following U.S. Pats;

Waterman No. 2,821,209 Jan. 28, 1958; Martin No.

2,926,690 Mar. 1, 1960; Foster No. 3,060,959 Oct. 30, I962; Tillman No.3,476,141 Nov. 4, 1969. Each of the above patents disclose operablehydraulic flow control devices of the type intended to restrict orprevent fluid flow through a line upon the occurrence of an excessivefluid flow rate therethrough. Of the above U.S. Pats., No. 2,821,209,2,926,690 and 3,476,141 operate in an essentially similar manner. Amovable piston element is normally biased to a position axially spacedfrom a valve seat. The piston has an area exposed to upstream flow andthe spring force acting on the piston is sufficient to maintain thepiston spaced from the valve seat during normal flow conditions.

In the event of excessive flow across the device, which is indicative ofan excessive pressure drop thereacross, the pressure force acting uponthe upstream area of the piston will cause the piston to move againstthe resilient biasing force and cause the piston to seat axially on thevalve seat.

Foster, U.S. Pat. No. 3,060,959, operates in a generally similar mannerexcept that the resilient means biasing the piston towards a normallyopen position is eliminated by differential areas on the piston memberand the upstream pressure is stored in an annular chamber 14 in FIG. 1to cause the piston 9 to move against an axial valve seat 21 upon theoccurrence of an excessive pressure drop across the valve.

Each of the above patents discloses a movable piston member having arelatively high mass and which close by movement of the piston memberagainst an essentially axially directed valve seat. With the exceptionof Martin, U.S. Pat. No. 2,926,690, each of the above prior art devicesrequire relatively complex machining on either the movable piston or thevalve seat or both in order to obtain the proper operatingcharacteristics.

SUMMARY OF THE INVENTION The invention of the present application is amuch more simple and efficient flow control device than those disclosedin the prior art. The hydraulic fuse of the present applicationcomprises a body having a cylindrical bore therethrough, a hollowcylindrical piston member located within the bore adapted to cooperatetherewith to control the flow of fluid across the valve. The hollowcylindrical piston includes a closed end located toward the upstreamside of the valve and a plurality of radial openings through the sidewalls thereof transverse to the sliding axis of the piston. The pistonis normally resiliently biased to a full flow position whereat fluidflow through the transverse openings and the piston is unrestricted bythe walls of the cylindrical bore. During periods of excessive fluidflow, the pressure drop across the valve is such that the pressureacting upon the area of the closed end of the tubular piston causes thepiston to move against the biasing force of the resilient means therebypartially closing the transverse openings therein. As the tubular pistonmoves against the force of the resilient biasing means, the wall of thecylindrical bore and the valve body partially closes the transverseopenings through the cylindrical piston. This closing causes a furtherpressure drop and continued movement of the piston until the transverseopenings are completely closed and fluid flow therethrough prevented.

A regulated flow opening may be provided through the closed end of thepiston member to permit a regulated quantity of fluid flow even thoughthe transverse openings are completely closed. This feature is desirablewhere the nature of the hydraulic system in which the fuse is to beinstalled requires a leakage flow through the fuse even though thehydraulic system has failed. One example of such a system would be inthe area of load raising hydraulic systems where leakage is desirable inorder to slowly lower the load to the floor rather than have it remainsuspended while workmen repair the failure.

BRIEF DESCRIPTION OFTHE DRAWING The drawing discloses a longitudinalsection through a hydraulic fuse embodying the features of the presentinvention.

DESCRIPTION OF A PREFERRED EMBODIMENT In the drawing there is shown alongitudinal section through a hydraulic fuse 10 which is adapted to beconnected in a hydraulic line having a normal directional fluid flowfrom left to right in the drawing and as indicated by the direction ofthe arrows. The hydraulic fuse 10 comprises a body 12 having a firstinlet bore 14 therein. Adjacent the inlet bore 14 is a flow control bore16 of somewhat reduced diameter. Toward the outlet end of the body 12 isa third cylindrical bore 18 having a diameter larger than the diameterof the flow control bore 16. The bores 14, 16 and 18 define a fluid flowpath through the body 12. Located within the body 12 is a piston member20. The piston member 20 includes a cylindrical thin walled tube portion22 hav-' ing a plurality of transverse openings 24 therein. The totaleffective flow area of these openings 24 is approximately equal to theflow area of the bore of the tube 22. The cylindrical tube portion 22 isclosed at one end 26 except for a regulated fluid flow passage 28therethrough and is of a diameter to provide a slip fit with the controlbore 16 when disposed therein. Located at another portion on the thinwalled tube portion 22 is a radially extending flange 30 which islocated within the bore 18 of the body 12 and is normally biased by acoil spring 32 into engagement with a shoulder 34 defined by the body 12between the bores 16 and 18. The shoulder 34 limits the movement of thepiston member 20 toward the left in the drawing. The spring 32 issupported on an annular washer 36 also located within the bore 18 of thebody 12. The washer 36 is in turn supported within the bore 18 of thebody 12 by an annular snap ring 38 which cooperates with a groove 40 inthe 4 body 12 of the hydraulic fuse 10. The spring 32 is given apredetermined preload so that the piston member 20 is normally biasedagainst the shoulder 34 of the body 12 to permit a predetermined flow offluid across the valve from left to right in the drawing withoutrestriction. Thus there is substantially no pressure drop across thefuse during normal flow rates.

However, if a flow rate across the valve becomes excessive, as forinstance when a hydraulic line ruptures downstream, there will existdownstream of the transverse openings 24, a pressure drop of suchmagnitude that the difference in pressure upstream of the openings 24and that downstream of the openings 24 is sufficiently great whenmultiplied by the differential areas of the closed end 26 of the pistonmember 20 that the piston member 20 will be moved toward the right inthe drawing against the force of the spring 32. As the piston memberbegins to move toward the right, the cylindrical bore 16 of the bodymember 12 will cover a portion of the transverse openings 24 therebycreating an even larger pressure drop between the upstream anddownstream fluid in the valve thereby creating an even greater tendencyof the piston member 20 to move to the right and restrict fluid flowtherethrough. The piston member 20 will continue to move under theeffects of excessive flow until the transverse openings 24 arecompletely within the bore 16 of the body 12 and fluid flow therethroughprevented.

In the embodiment shown in the drawing, the closed end 26 is providedwith a restrictive or secondary flow orifice 28 therethrough. This willpermit the flow of a predetermined quantity of fluid across the valveeven though the transverse openings 24 are completely covered by thebore 16 of the body 12. Upon alleviation of the excessive flow, thepressure force on the closed end 26 of the piston member 20 will fallbelow the returning force of the spring 32 and the piston member 20 willreturn to its fully opened position.

The use of a thin wall tubular piston member and radially extending flowcontrol orifices therein greatly simplifies the valving structurerequired to regulate flow across the valve. in fact, no valve seat isrequired. Flow regulation is accomplished in a very simple and directmanner using the internal bore 16 of the body 12 to regulate flowthrough the openings 24 in the piston member 20 as the piston membermoves to the right in response to excessive fluid flow. Further, the useof a tubular piston permits accurate control over the inertia of thepiston and permits rapid and precise control of fluid flow by use of arelatively low mass piston member.

Further, the use of a tubular piston member having radial openingstherein permits a greatly simplified regulation of flow of the typedesired in the hydraulic fuse because movement of the piston member 20toward the right in the drawing in response to an excessive flow may beused to immediately close portions of the openings 24 so that thepressure drop across the piston member increases even further therebytending to move the piston member 20 against the force of a spring 32 toa fully closed position more rapidly and positively than could beexpected in the prior art devices without complex machining operationshaving been performed on the piston members of the prior art devices.

The use of a thin walled cylindrical piston member furtherfacilitatesthe provision of a flow path through the piston which is most nearlycompatible with the other flow areas in the hydraulic system therebyreducing or minimizing the pressure drop in the hydraulic system due tothe hydraulic fuse l and thus increasing the efficiency of operation ofthe hydraulic system over hydraulic systems using prior art hydraulicfuses. The flow areas across the pistons of the prior art devices areinherently limited by the structure used. It is possible by the use ofthe concept of the present invention of providing a cylindrical thinwalled tube as the piston member to obtain a flow area across the pistongreater than that possible in operable axial piston type hydraulic fusessuch as those known in the prior art. This is extremely importantbecause a hydraulic fuse must provide minimum restriction to flow duringnormal operation in order to preserve efficiency of the hydraulicsystem. On the other hand, the fuse must provide some restriction toexcessive flow in order to create the pressure drop necessary to actuatethe fuse.

A further advantage of a relatively thin walled tubular piston member isthat any change in momentum of the hydraulic fluid occurring across thepiston due to a restriction in flow occurs transversely to the axis ofpiston movement and therefore has no effect on operation of thehydraulic fuse.

I now claim:

1. A hydraulic fuse comprising:

a body member having a circular bore defining a fluid flow paththerethrough,

a thin-walled tubular cylindrical piston member loosely received withinsaid bore for sliding movement relative thereto between a first positionand a second position, i

said tubular piston member being open at the downstream end thereof andclosed at the upstream end and having an opening in a radial wallportion thereof adjacent said closed end,

said radial wall portion extending beyond said bore to provide a flowpath through the fuse which is radial to said tubular piston at saidopening in a radial wall adjacent the upstream end thereof and axial tosaid piston at the downstream end thereof,

said radial wall portion cooperating with said bore to reduce the areaof the flow path through the fuse when the piston moves from said firstposition toward said second position, and

means providing a predetermined biasing force between the body and thepiston urging the piston toward said first position whereby a fluid flowrate beyond a preselected level in the direction from said firstposition toward said second position will move the piston to said secondposition thereby closing off said flow path.

2. The hydraulic fuse of claim 1 wherein said body member has acounterbore axially disposed at one end of said bore, and said radialwall portion extends into said counterbore;

3. The hydraulic fuse of claim 1 wherein said body member has acounterbore axially disposed at each end of said bore, said tubularpiston member has a flange at one end thereof and said biasing meanscomprises a spring engaging said flange, one of said counterborescooperating with said radial wall portion of said tubular member todefine a portion of the flow path through the fuse, while the other ofsaid counterbores provides a housing for said spring and said flange andmeans for said spring to act against to bias said flange and said pistonto said first position.

4. The fuse of claim 1 wherein said tubular piston member has asecondary flow opening in the closed end thereof providing a leakageflow path through the fuse when said piston is in said second position.

5. The fuse of claim 1 wherein the area of the opening in the radialsurface is substantially equai to the area defined by the internal wallof the tubular piston.

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1. A hydraulic fuse comprising: a body member having a circular boredefining a fluid flow path therethrough, a thin-walled tubularcylindrical piston member loosely received within said bore for slidingmovement relative thereto between a first position and a secondposition, said tubular piston member being open at the downstream endthereof and closed at the upstream end and having an opening in a radialwall portion thereof adjacent said closed end, said radial wall portionextending beyond said bore to provide a flow path through the fuse whichis radial to said tubular piston at said opening in a radial walladjacent the upstream end thereof and axial to said piston at thedownstream end thereof, said radial wall portion cooperating with saidbore to reduce the area of the flow path through the fuse when thepiston moves from said first position toward said second position, andmeans providing a predetermined biasing force between the body and thepiston urging the piston toward said first position whereby a fluid flowrate beyond a preselected level in the direction from said firstposition toward said second position will move the piston to said secondposition thereby closing off said flow path.
 2. The hydraulic fuse ofclaim 1 wherein said body member has a counterbore axially disposed atone end of said bore, and said radial wall portion extends into saidcounterbore.
 3. The hydraulic fuse of claim 1 wherein said body memberhas a counterbore axially disposed at each end of said bore, saidtubular piston member has a flange at one end thereof and said biasingmeans comprises a spring engaging said flange, one of said counterborescooperating with said radial wall portion of said tubular member todefine a portion of the flow path through the fuse, while the other ofsaid counterbores provides a housing for said spring and said flange andmeans for said spring to act against to bias said flange and said pistonto said first position.
 4. The fuse of claim 1 wherein said tubularpiston member has a secondary flow opening in the closed end thereofproviding a leakage flow path through the fuse when said piston is insaid second position.
 5. The fuse of claim 1 wherein the area of theopening in the radial surface is substantially equal to the area definedby the internal wall of the tubular piston.